The development of an implantable glucose sensor could provide opportunities for a closer control of glucose levels in diabetes than is now possible. Glucose sensor work using catalytic metal sensor based upon platinum has been under development in our laboratories for the past several years, and considerable progress has been made in improving the sensitivity, short term stability, and selectivity of the sensor. The purpose of the proposed research is to improve the longevity of electro-catalytic glucose sensors based on platinum. Maintenance of a sensor response at a constant level over an extended period of time is desirable, since it avoids the need for frequent recalibration. Phase I work in this program has clearly demonstrated that specially formulated polymer bonded platinum black electrodes show an order of magnitude improvement in stability. The proposed Phase II program aims to further optimize the electrode structure, develop a proper biocompatible outer membrane, and conduct 72 hour in vivo tests to demonstrate the technology.